IMPACT OF DIFFERENT BUFFERS ON MEASURES OF POST-RUMINAL FERMENTATION
Date
2017-05
Authors
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Publisher
University of Delaware
Abstract
With an emphasis on increased production, dairy cow rations have shifted to
higher energy feeds with higher concentrations of starch. High starch rations are
rapidly digested within the rumen, causing pH levels to decline and ruminal acidosis.
However, there is also increased passage of fermentable carbohydrates to the
intestines which can lead to intestinal acidosis. The purpose of this study was to
evaluate the effects of different buffers on the severity of hindgut acidosis. In a 5 x 5
Latin square design, ten multiparous cows were randomly assigned to treatments of a
high starch diet as the control (CON), the control diet supplemented with sodium
bicarbonate (FSB), calcium carbonate (FCC), or calcium carbonate and magnesium
oxide (FCCM), or the control diet with abomasally infused encapsulated sodium
bicarbonate (ISB). It was hypothesized that the ISB, FCC, and FCCM treatments
would be effective in ameliorating hindgut acidosis. Cows were housed in a tie-stall
barn and were fed twice a day for ad libitum intake. Cows were infused twice daily
with corn starch suspended in 1.5 L of tap water. Rumen fluid and fecal samples were
collected on day 7 of each period at 4-hr intervals beginning at 6:30 am and ending at
2:30 am on the following day for measurement of pH, volatile fatty acids (VFA), and
lipopolysaccharide (LPS). Feed samples were collected on day 7 of each period after
the 6:30 am sampling. Milk samples were collected on day 7 during the morning and
afternoon. Treatment did not affect rumen pH, but fecal pH was higher in the FCCM
group (pH 6.64; P < 0.001) than in the CON group (pH 6.47; P<0.001). Time affected
total rumen VFA, but not rumen lactate, acetate, propionate, isobutyrate, valerate,
isovalerate, or total VFA (P > 0.10). There were no effects of treatment on fecal
lactate, butyrate, isobutyrate, valerate, or isovalerate (P > 0.10); however treatment
affected acetate (P = 0.04) and propionate (P= 0.03) and tended to affect total VFA (P
= 0.07). Total VFA were greater for FCC and FCCM compared to CON (P = 0.03 and
0.007, respectively). Similarly, acetate was greater for FCC and FCCM compared to
CON (P = 0.02 and 0.003, respectively), and propionate was greater for FCC and
FCCM compared to CON (P = 0.01 and 0.005, respectively). In addition, fecal acetate
was lower in FSB compared to FCCM (P = 0.05). The contrast of CON vs. (ISB +
FCC + FCCM) was also significant for total VFA, acetate, and propionate, due to
lower VFA for CON vs. the proposed post-ruminal buffers. Fecal dry matter was
affected by time (P < 0.001), due to the lowest dry matter at 0 h (13.0%), intermediate
dry matter at 4, 12, and 16 h (13.4 to 13.8%), and greatest dry matter at 8 and 20 h
(14.4 and 14.5%, respectively, however treatment did not affect fecal dry matter. The
data suggest that FCC and FCCM have postruminal buffering capability, but data on
LPS levels and digestibility (pairing of feed and fecal composition data) will be
needed to support this conclusion.
Description
Keywords
Animal Science, buffers, post ruminal fermentation